Geotechnical issues on airport projects constructed in Japanese coastal area

摘要

This paper introduces some important geotechnical issues evolved and how they were faced in constructing three of such coastal airports constructed on soft land reclaimed, namely, Tokyo International Airport (TIA), Kansai International Airport (KIA) and Central Japan International Airport (CJIA). As the TIA was constructed on the reclaimed land, which consists of dredged slurry and waste soil, the large scale ground improvement had been carried out. Recently, a new ground improvement technique has been developed and used in this project to strengthen the seismic resistance of runway against the anticipated strong earthquake motion. In addition, the light-weight soil method was developed and applied in the new taxi-way, which were constructed on existing railway tunnel. KIA was constructed in an artificial island of 5km offshore in Osaka Bay. The 1st phase construction completed in 1994, when the airport opened with a single runway. The issues related to the 2nd phase construction project, which started July 2000 were introduced. The improvement of Holocene clay layer and the prediction of settlements of deep Pleistocene cay layers are key problems in this project. The construction of CJIA also started in August 2000. CJIA is to be constructed on the artificial island in Ise Bay. A large volume of cement treated clay made by the pneumatic flow mixing method are to be used as the fill in the first time. As the clays used for the cement treatment are taken by dredging of navigation channel in Nagoya Port nearby, the use of pneumatic flow mixing method in CJIA will be a unique case as a large scale recycling of waste soils.